import java.util.List;

public class MyDoublyLinkedList implements IDoublyLinkedList{

    static class ListNode {
        //节点数据
        public int val;

        //节点的前驱
        public ListNode prev;

        //节点的引用
        public ListNode next;


        public ListNode(int val) {
            this.val = val;
        }
    }

    //储存链表头节点的引用
    public ListNode head;

    //储存链表尾节点的引用
    public ListNode last;


    //------------------------------------------无头双向链表实现------------------------------------------

    //头插法
    @Override
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else{
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    //尾插法
    @Override
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else{
            last.next = node;
            node.prev = last;
            last = node;
        }
    }

    //任意位置插入,第一个数据节点为0号下标
    @Override
    public void addIndex(int index, int data) {
        if(index < 0 || index > size()){
            throw new CheckPosException("索引不合法");
        }

        if(index == 0) {
            addFirst(data);
            return;
        }

        if (index == size()){
            addLast(data);
            return;
        }

        ListNode cur = searchIndex(index);
        ListNode node = new ListNode(data);

        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;


    }

    private ListNode searchIndex(int index){
        ListNode cur = head;
        while(index != 0){
            cur = cur.next;
            index--;
        }
        return cur;
    }

    //查找是否包含关键字key是否在单链表当中
    @Override
    public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null){
            if (cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //删除第一次出现关键字为key的节点
    @Override
    public void remove(int key) {
        ListNode cur = head;
        while(cur != null){
            if (cur.val == key){
                if (cur == head){
                    head = head.next;
                    if (head != null){
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if (cur.next == null){
                        last = last.prev;
                    }else {
                        cur.next .prev = cur.prev;
                    }

                }
                return;
            }
            cur = cur.next;
        }
    }

    //删除所有值为key的节点
    @Override
    public void removeAllKey(int key) {
        ListNode cur = head;
        while(cur != null){
            if (cur.val == key){
                if (cur == head){
                    head = head.next;
                    if (head != null){
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if (cur.next == null){
                        last = last.prev;
                    }else {
                        cur.next .prev = cur.prev;
                    }

                }
            }
            cur = cur.next;
        }

    }

    //得到单链表的长度
    @Override
    public int size() {
        int count = 0;
        ListNode cur = head;
        while(cur != null){
            count++;
            cur = cur.next;
        }
        return count;
    }

    @Override
    public void display() {
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }

    @Override
    public void clear() {
        ListNode cur = head;
        while (cur != null){
            ListNode curN = cur.next;
            cur.prev = null;
            cur.next = null;
            cur = curN;
        }
        head = null;
        last = null;

    }

}
